Study on Auto-Ignition Characteristics of Gasoline-Biodiesel Blend Fuel in a Rapid Compression Expansion Machine

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1 Available online at ScienceDirect Energy Procedia 05 (207 ) The 8 th International Conference on Applied Energy ICAE206 Study on Auto-Ignition Characteristics of Gasoline-Biodiesel Blend Fuel in a Rapid Compression Expansion Machine Vu Dinh Nam a, Myung Taeck Lim b, Ocktaeck Lim a* a School of Mechanical Engineering, University of Ulsan, Ulsan , Republic of Korea b Department of Mechanical Engineering, Graduate School of Chonnam National University, Gwangju , Korea Abstract Compression ignition (CI) engines are widely utilized on various vehicles nowadays. The CI engines have higher energy conversion efficiency in general than spark ignition (SI) engines mainly due to high compression ratio, lean stratified charge, and no throttling. This study aims to secure stable auto ignition and combustion of gasoline/biodiesel blend fuel when applied to a direct-injection compression ignition engine. Influences on auto ignition and combustion behaviors of various ambient temperature from 600 to 800 K and different biodiesel fractions were studied in a rapid compression expansion machine (RCEM) at compression ratio of. Increased biodiesel fraction caused the ignition delay time to shorten. This is because the biodiesel has a better flammability than gasoline. The experimental results are compared with those from numerical simulation using CHEMKIN-PRO and surrogate fuels, and they are in good agreement The The Authors. Authors. Published Published by Elsevier by Elsevier Ltd. This Ltd. is an open access article under the CC BY-NC-ND license ( Selection and/or peer-review under responsibility of ICAE Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. Keywords: Ignition delay, Rapid Compression Expansion Machine, Gasoline/biodiesel blend fuel, Auto ignition, Temperature combustion. Introduction The compression ignition (CI) engine has higher energy conversion and energy efficiency in comparison with a spark ignition (SI) engine because the CI engine has higher compression ratio than the SI engine []. For that reason some studies have been focused on efforts the examination using blend fuels is promising way to control emission and improve efficiency in Homogeneous Charge Compression Ignition (HCCI), Premixed Charge Compression Ignition (PCCI) [2]. Some studies [3], [4] studied pure gasoline and its blend fuels with diesel in HCCI engine. They found that increasing diesel fuel fraction the intake temperature requirement is lower to obtain the HCCI operation and get low emission. And these studies shown that stability for gasoline diesel blend fuels is better than the pure gasoline. However increasingly stringent emission standards, limited availability of fossil fuel reserves, and global warming * Corresponding author. Tel.: ; fax: address: otlim@ulsan.ac.kr The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. doi:0.06/j.egypro

2 790 Vu Dinh Nam et al. / Energy Procedia 05 ( 207 ) with increasing greenhouse gas is a serious problem. The scientific community has been attempting to develop clean technologies, the parallel work is utilization of next-generation alternative fuels is greatly expected [5], [6]. Biofuel is considered as the renewable energy source with the highest potential to contribute to the energy needs of modern society for both the developed and developing economies worldwide [7]. For this reason, in this study biodiesel is chosen an alternative fuel to diesel in gasoline/biodiesel blend fuel to investigate. In a CI engine, auto ignition of the air-fuel mixture is necessary. The proper fuel must be chosen that will auto ignite at the precise time in engine cycle. It is very important to have knowledge and control of ignition delay of the fuel. Because of improper ignition delay in a CI engine, the combustion phase is changed, which can cause negative effects. The one of common symptom of the negative effects is decreased power output. The improper ignition delay also lead to rise to the phenomena known as knocking which can cause instability of combustion and decreasing extremely the life of the engine [8]. Because the specification for the gasoline/biodiesel blend fuel is lack of information. And a fuel is used with unknown and varying ignition delay that can reduce the life of the engine [9]. As such, it is important to better understand the ignition delay qualities of gasoline/biodiesel blend in order to apply to the CI engine. The objective of this study was to contribute to the basic knowledge concerning gasoline/ biodiesel blend fuel ignition delay at diesel engine conditions using a rapid compression expansion machine (RCEM). Experiments are conducted to determine the ignition delay. The finally gasoline/biodiesel blend fuel was calculated in CHEMKIN-PRO and comparing with experimental results. Effects of various ambient temperatures, different biodiesel friction etc. on auto ignition and combustion behaviors of biodiesel/gasoline blend fuels were studied in the RCEM in range from 600 to 800 K at compressed ratio of. 2. Experimental method 2.. Rapid Compression Expansion Machine Specification In this study, the RCEM was used to investigate auto ignition and combustion characteristics of gasoline/biodiesel blend fuels which was injected into a cylinder of the RCEM. The RCEM was installed in a fully instrumented test cell, with all the auxiliary facilities required for its operation and control, as is illustrated in Fig.. The bore and stroke of RCEM are mm and 450 mm, respectively. The volumetric compression ratio (CR) of the RCEM can be varied from CR = 0 to CR = 23.5 by changing the clearance volume. The RCEM was equipped with a common-rail flexible injection hardware which is able to perform up to 600 bar Mixture preparation Gasoline/biodiesel blend fuel was chosen as the fuel. The experimental study was carried out using four fuel samples including GB5, GB0, GB5 and GB 20. The fuel compositions are listed by table Test conditions Table. Blend fuel compositions (% vol) No Fuel Component (%vol) Density (5 C-kg/m3) GB5 Gasoline 95% + Biodiesel 5% GB0 Gasoline 90% + Biodiesel 0% GB5 Gasoline 85% + Biodiesel 5% GB20 Gasoline 80% + Biodiesel 20% 757.

3 Vu Dinh Nam et al. / Energy Procedia 05 ( 207 ) Table 2 shows the experimental conditions for fuel auto ignition measurement. In-cylinder temperature at the start of injection T inj is calculated from a state equation with in-cylinder volume and pressure. In case that a compression ratio of RCEM is, in-cylinder temperature at the top dead center (TDC) is 947 K if it is assumed that compression stroke is adiabatic. Actually in-cylinder temperature was calculated with the measured pressure was 690 K, which is much lower than the adiabatic temperature. It would be supposed that this temperature difference is derived the compression speed of RCEM. The rotation speed of RCEM used in this study was about 200 rpm and it took long time for the compression stroke. Then heat losses from the cylinder walls couldn t be neglected Definition of auto ignition delay Fig. 2 shows definition of auto ignition delay, combustion phase and control signal of the injector. The auto ignition delay is defined as the time (or crank angle) interval between the start of injection and the start of combustion. The start of injection is determined by measuring the current to the injector solenoid, and adding an additional delay due to the physical operation of the injector, which is determined through calibration. In this study, injection delay is 0.4 ms. The start of combustion is defined as a time after incylinder pressure depart from motoring pressure exceeds 0% Chemical kinetic calculation The calculation were conducted under non-dimension by CHEMKIN-PRO software. A onecomponent surrogate was considered consisting of methyl decanoate for the chemical representation of the biodiesel fuel [0]. Three-component surrogate of Vanhove et al. (2006) was considered consisting of iso-c8h8, C6H2-, C6 H5CH3 = 47/8/35 for the chemical representation of the gasoline fuel []. Creation of gasoline and biodiesel model. Fig.. Schematic diagram of rapid compression expansion machine Reaction model of gasoline/biodiesel blended fuel have not been investigated. The Reaction model of Gasoline/Biodiesel blend fuel was created in this study. So the reaction model for gasoline/biodiesel blend fuel was created by combination from reaction model for gasoline [3] and reaction model for biodiesel [2]. In the biodiesel model, some reactions were duplicated from those in the gasoline model, whereas reactions in the gasoline model were unique. In this case, the gasoline scheme represented the

4 792 Vu Dinh Nam et al. / Energy Procedia 05 ( 207 ) basic scheme. The reactions of biodiesel were not found in the gasoline model were combined with those in the gasoline model. Finally, the reaction scheme was created. Table 2 experimental conditions for gasoline/biodiesel blend fuels auto ignition measurement. Case Case 2 Fuel GB5, GB0, GB5 and GB20 Intake gas temperature [K] Injection pressure P inj [bar] 800 Injector specification Four holes, nozzle-hole diameter de [mm] Equivalence crank speed [rpm] 200 Compression ratio Premixed gas reactants Air Equivalence ratio 0,5 Injection timing t inj [deg.atdc] -2.0±0.25 Ambient gas temperature at start of injection T inj [K] Ambient gas pressure at start of injection pa [bar] 8 8 Validation The amount is varied to compare between the combined gasoline/biodiesel surrogate and Vanhove s model or LLNL model. The amount of gasoline is % and biodiesel is 0% for comparing Vanhove s model. And the next, biodiesel is % and gasoline is 0% for comparing LLNL s model. The comparisons show a good agreement to validate the gasoline/biodiesel surrogate and Vanhove s model or LLNL model used in this study. Validation 0 Ignition delay [ms] 0 Gasoline surrogate [Vanhove's model] Biodiesel surrogate [LLNL's model] Gasoline/biodiesel surrogate Time [s] /K Fig. 2 Definition of auto ignition delay and combustion phase 3. Results and discussion Results from chemical kinetic reaction Fig. 3 shows the comparison on ignition delay time between gasoline/biodiesel surrogate and LLNL s model or Vanhove s model at temperature range from 650 to and pressure at 8 bar.

5 Vu Dinh Nam et al. / Energy Procedia 05 ( 207 ) Fig. 4 shows the results of calculations in comparison for the ignition delay time, versus the inlet air temperature, for the various gasoline/biodiesel ratios. Ignition delay times decreases with increasing biodiesel in gasoline/ biodiesel blend fuel. However, some differences were observed between 650 K and K, and the difference of the ignition delay due to the effect of biodiesel fraction, which has a high ignition delay at low biodiesel friction. Effects of biodiesel fraction on auto ignition delay time. Experiments were carried out to measure the ignition delay times of gasoline/biodiesel blend fuels in different proportions. In this study, ignition delay times of some kinds of gasoline/biodiesel blend fuels (5%, 0%, 5% and 20% volume of Biodiesel) were measured for air-fuel ratio (ɸ=0.5) of 0.5 at compressed pressures of 8 bar, in the compressed temperature of 70K. A total five fuel samples of ignition delay time for biodiesel, GB20, GB5, GB0, and GB5 are plotted in Fig.5. From the average ignition delay period, it is observed in 0.76 CA, 2.64 CA, 5.25 CA, 4.09 CA and 4.76 CA respectively for biodiesel, GB20, GB5, GB0, and GB5. With the decrease of biodiesel fraction, the ignition delay period is increasing. Ignition delay [ms] 0 0 Fuels Biodiesel Gasoline GB5 GB0 GB5 GB /K Fig. 4. Ignition delay time for pure biodiesel, pure gasoline and GB Comparison of experimental investigation and simulation Fig. 5 Experiment pressure traces obtained at 8 bar and ɸ=0.5 for pure biodiesel, GB5, GB0, GB5, and GB20 Fig. 6 and fig. 7 show the comparison of total ignition delays obtained from the present RCEM experiments and simulations, at varying temperature, air-fuel ration of 0.5 and compressed pressures of 8 bar. Fig. 6 illustrates the performance of the gasoline/biodiesel surrogate model in predicting the total ignition delay (solid line). Plus symbols present auto ignition measurement by the RCEM. Response of auto ignition delay measured by the RCEM is closer agreement when compared to the numerical results. Fig. 7 further plots and compares the experimental and simulated auto ignition delay at varying temperature at air-fuel ration of 0.5 and compressed pressures of 8 bar for GB20. The simulated auto ignition delays are also closer agreement when compared to the experimental results.

6 794 Vu Dinh Nam et al. / Energy Procedia 05 ( 207 ) Igntion delay time [second] 0 GB 0 Numerical result Experimental result Ignition delay time [second] 0 GB 20 Numerical result Experimental result Temperature [K] Fig. 6 Comparison of ignition delay responses of GB0 and surrogates at 8 bar, ɸ = Conclusions Fig. 7 Comparison of ignition delay responses of GB20 and surrogates at 8 bar, ɸ =0.5 This mainly experimental study investigated the auto ignition delay of gasoline/biodiesel blend in the RCEM. The study focuses on four fuel blends of GB5, GB0, GB5 and GB20. In addition, the CHEMKIN-PRO software was used to examine the effects of biodiesel fraction on auto ignition delay of the blended fuel. Conclusions are drawn as follows: - Auto ignition delay time of gasoline/biodiesel blend fuel is largely affected by biodiesel fraction. - Higher ambient temperature at injection time decreases auto ignition delay time of gasoline/biodiesel blend fuel. - Gasoline/biodiesel surrogates properly represent auto ignition delay characteristics of the blend fuel at any level of biodiesel fraction. - Increased biodiesel fraction causes the ignition delay time to get shorter. Acknowledgements This research was financially supported by the Ministry of Education (MOE) and National Research Foundation of Korea (NRF) through the Human Resource Training Project for Regional Innovation and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (202RAA044855). References Temparature [K] [] John B.LHeywood. Internal combustion engine fundamentals. [2] J. Li, W.M. Yang, H. An, S.K. Chou. Modeling on blend gasoline/diesel fuel combustion in a direct injection diesel engine. Applied Energy 60 (205) [3] Shaohua Zhong, M.L. Wyszynski, A. Megaritis and D. Yap. Experimental Investigation into HCCI Combustion Using Gasoline and Diesel Blended Fuels. SAE Technical Paper Series [4] Jesus Benajes, Alberto Broatch, Antonio Garcia and Luisa Monico Muñoz. An Experimental Investigation of Diesel-Gasoline Blends Effects in a Direct-Injection Compression-Ignition Engine Operating in PCCI Conditions. SAE International 0.427/

7 Vu Dinh Nam et al. / Energy Procedia 05 ( 207 ) [5] Taku Tsujimura, Keita Mitsushima, Ryuichi Hata, Yoshiroh Tokunaga, Jiro Senda, Hajime Fujimoto. Study on Characteristics of Auto-ignition and Combustion in Hydrogen Jet with A Rapid Compression and Expantion. Journal of Loss Prevention in the Process Industries 35 (20) [6] Goutham Kukkadapu, Kamal Kumar, Chih-Jen Sung, Marco Mehl, William J. Pitz. Experimental and surrogate modeling study of gasoline ignition in a rapid compression machine. Combustion and Flame 59 (202) [7] Communication from the Commission. Energy for the future: renewable sources of energy. COM(97)599 final (26//997) [8] Casey Allen, Elisa Toulson, Daniel Tepe, Harold Schock, Dennis Miller, Tonghun Lee. Characterization of the effect of fatty ester composition on the ignition behavior of biodiesel fuel sprays. Fuel (203) [9] Adam M. McNeilly. Ignition Delay of JP-8 at Diesel Engine Conditions. University of Wisconsin Madison 20 [0] Olivier Herbinet, William J. Pitz, Charles K. Westbrook. Detailed chemical kinetic oxidation mechanism for a biodiesel surrogate. Combustion and Flame 54 (2008) [] Marco Mehl, William J. Pitz, Charles K. Westbrook, Henry J. Curran. Kinetic modeling of gasoline surrogate components and mixtures under engine conditions. Proceedings of the Combustion Institute 33 (20) Biography Ocktaeck Lim received his B.S. and M.S degrees in Mechanical Engineering from Chonnam National University, Korea, in 998 and 2002, respectively. He received his Ph.D. degree from Keio University in Dr. Lim is currently a Professor at the School of Automotive and Mechanical Engineering at Ulsan University in Ulsan, Korea. Dr. Lim s research interests include Internal Combustion Engines, Alternative Fuel and Thermodynamics. Vu Dinh Nam was born in Viet Nam, in 985. He received his B.S and M.S degrees in Mechanical Engineering from Hanoi University of science and technology in 2009 and 204 respectively. Now, he pursues his PhD s in Mechanical and Automotive Engineering under the supervision of Professor Ocktaeck Lim at the School of Mechanical Engineering at University of Ulsan Republic of Korea.